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Using oil w/ good compression...help

2002 2.5L Forester, SOHC w/ 187k. Just had new head gasket and timing belt 3k ago. Using 1 quart oil/ 300 miles. Noticed immediately after head gasket and timing belt change. No external leaks, no oil into coolant. No noticeable smoking or burning oil smell. Engine performance seems normal; MPGs about normal 26 on hwy and seems to have power climbing. I do have a bad catalytic converter but upstream O2 sensor is new and no codes for it but do have a code for the downstream one.

Did not have problem before head gasket replacement. &nbsp;Added Seafoam into crankcase and changed oil and filter after 200 miles.

Hard to tell how much oil it used before HG as I was losing oil as an external leak....but I would have to put in about 1 quart every 3000 miles or so. I did also change the PCV value, checked all the PCV related hoses and checked the air filter. Is there anything else I can check as far as the PCV system?

I had a clean air filter so I was assuming I was not losing oil (as blow-by) thru the PCV system.

Have you changed the PCV valve and checked the PCV hoses to make sure they are not clogged?

He said 1 qt every 300 miles, as I read it.

Were the valves ground? In my experience, new heads (valves) on old rings often results in excess oil consumption. The combination of extra blowby and additional vacuum may both aspirate oil and draw it into the intake or up past the rings.

I have an engine in the shed that has new heads, old bottom end, that used a quart per tank and has exces "piston slap" Seems to me tight rings would reduce that noise too.

Engine not cooked from blow HG, caught it right away. Car does not smoke or at least it's not noticeable if it does...no burning oil smell either. It does have a bad catalytic converter; waiting to diagnose oil consumption problem before I change the cat.

My best guess is bad oil control rings, too much oil consumption for bad valve seals. Any other ideas I'm all ears don't really want to spend $ for rebuilt engine.

I've seen EJ's burn lots of oil when the o-ring that seals the vent tube that submerges in the back corner of the oil pan. Can't quite figure how, but twice now pulled engines for HORRIBLE oil consumption, and BOTH had no o-ring on that tube.

I believe it's supposed to be sealed and submerged in oil so no airflow moves up that tube. Serves as the drain back for any other oil in the PCV system, but when it's not sealed at the bottom it becomes a source of sucking oil/vapors from low in the engine instead of up high at the Valve covers.

I've seen EJ's burn lots of oil when the o-ring that seals the vent tube that submerges in the back corner of the oil pan. Can't quite figure how, but twice now pulled engines for HORRIBLE oil consumption, and BOTH had no o-ring on that tube.

I believe it's supposed to be sealed and submerged in oil so no airflow moves up that tube. Serves as the drain back for any other oil in the PCV system, but when it's not sealed at the bottom it becomes a source of sucking oil/vapors from low in the engine instead of up high at the Valve covers.

I am going after that one right away, on my shed engine. I'll report back.

Pluged oil ring oil feed holes drys out top side of cly wall and burns oil comp is good becuse is not a comp ring problem is oil ring problem the only fix is remove pistons clean ring groves and oil feed holes Knurll pistons rering and good to go. Or mabee two or 3 oil changes in a row might clear them

Maybe try some sea foam first. The compression isnt horrible so stuck/gummed/bad oil rings really are all thats left. What do the plugs look like?

I did try sea foam just in the crankcase and didn't notice any change. Changed the oil and filter after about 300 miles after the sea foam; as the oil was pretty dirty.

Was the oil pan removed and resealed during the headgasket?

I've seen EJ's burn lots of oil when the o-ring that seals the vent tube that submerges in the back corner of the oil pan. Can't quite figure how, but twice now pulled engines for HORRIBLE oil consumption, and BOTH had no o-ring on that tube.

I believe it's supposed to be sealed and submerged in oil so no airflow moves up that tube. Serves as the drain back for any other oil in the PCV system, but when it's not sealed at the bottom it becomes a source of sucking oil/vapors from low in the engine instead of up high at the Valve covers.

Not sure if the oil pan was removed when the HG was replace but I assume it was not unless it needs to come off to get the engine out. If the O-ring on tube is missing wouldn't the PCV valve and associated PCV hoses be oily?....They are clean.

Not sure if I mentioned....the plugs were clean (not oily) when I pulled them for the compression test.